The Donald is used to being the front-runner and Trump remains on top of the Republican Presidential race, nationally and in New Hampshire, but not in Iowa, and he's not happy.

FOX News' Rachel Sutherland reports:

Ted Cruz is the new number one in Iowa, ahead of the state's all-important caucuses in February. A new FOX poll finds Cruz leading Donald Trump, 28 to 26% and a poll from the Des Moines register shows Cruz with a ten-point lead.

Caucus-goers say both Trump and Cruz are most qualified to handle the economy and national security. On FOX News Sunday, Trump called Cruz a maniac who's not fit for the presidency.

(Trump) "I don't think he has the right temperament. I don't think he's got the right judgment."

Marco Rubio comes in third with 13%. Carson, who was the Iowa front-runner in October, is fourth with 10%.

In Washington, Rachel Sutherland, FOX News.